Flattening (reasonably) curly cherry board

-- 0 --

I am using a beautifully curled cherry board in the top of a 42" high countertop. The board is 3/4" thick, 7-1/2" wide by 74" long. Unfortunately it has a severe twist.

I don't have enough thickness to remove much wood in order to get rid of the twist. I only need to get it close to flat since I can attach it to the wall structure below to help pull it flat. I am thinking that a series of closely spaced, cross-cut kerfs across the bottom of the board will weaken the board enough to let the board be pulled flat during attachment. Good idea? If so, how deep should I saw the kerfs?

If I was you, I would find another use for this board. A board that is bowed relative to the edge or face can sometimes be fastened down flat. A "severely twisted" board will be hard to fasten down flat. You could join the board flat then re-saw or plane the board to uniform thickness and laminate it to a piece of mdf. You would have to laminate a same thickness and type (cherry) board to the other side of the mdf or it will cup

Monte:
Read Geoff's response over and over. The only way to use this plank is to either let it be twisted because whatever you try to do to flatten it will only come back to haunt you! Or resaw it into veneer! The option of sawing 2 slices of veneer and laminating it onto an MDF substrate would be the best and in my book the only way to do this job without a call back next winter when the air is once again dry! Edge the MDF with cherry from a nice straight plank and if the end grain is going to show cut enough end grain to cover the end(s) of the MDF. Saw the veneer so when sanded out it is 1/16th inch thick, cut enough to veneer both sides of the MDF and use PVA or another hard adhesive UF would be good too. Do not use contact cement as it will give the countertop a dead feel when you tap your knuckle on it.

I cut all my own veneer for table tops and desk tops and often from really badly twisted boards. In nearly 30 years I've never had a failure and my clients are in awe of the amazing grain patterns and not in awe of how their furniture twisted itself to pieces! Have fun with it and if you don't want the wood drop me a note maybe we can work a deal.

Only place I'd disagree is with veneering it onto mdf. I wouldn't recommend it for a c-top that could likely see liquid spills over time. Not to mention it's more work than needed. No I'd re-saw the curly into thick veneers….maybe 1/8" or just a bit thinner. Then I'd glue it in a vac press to both sides of a nice flat piece of plain cherry, preferably closer to 1-1/4" thick for my taste.

Other than that I agree, trying to force a piece of wood into a position is a very risky procedure.

Well, Monte, I guess I'm going to be the contrarian this time. I think you can do what you want, but not "cross-grain" as you state.

If the board it twisted, it probably also has a spiraling grain as well as other figure, which leads to the twisting as it dried.

What I would do, is to make the kerf run diagonally along the bottom down it's length parallel to the grain, from one corner to the opposite corner at the other end.

Cupping is a weak force, so if you have plenty of wood on either side to draw it down, that shouldn't be that hard to do. However, you do need to allow it to move due to the changing MC of the seasons.

I could be wrong since I can't see the actual board and situation. Just keep in mind, that if you make it too tight, and it tries to shrink, it will likely split up from the weakest of one of those kerfs.

Gentlemen, thank you. I assume all of you are speaking from experience.

I was about to commit to jointing and resawing it into a veneer when Keith gave me hope that my first thought to kerf the bottom may work. When I say "severe twist" I mean opposite corners are about 5/8" out of plane...over a 74" span. The convex face would be the show face. I am able to clamp it flat onto a bench which made me think that I could relieve some stress by kerfing it.

The board will be edge joined to other boards to form a 19" x 72" top for a freestanding wall 42" high to divide an office.

If you have any thicker lumber around, like a 2x8 SYP or something that you can clamp it down to. Then apply some heat to that convex face, drying only that side, may get it back to flat before you do anything else.

It is easier to hold something flat than to try bending it. Also, you will need a straight edge square to the face before you can get a good glue line to join the boards next to it. This is not easy while it is twisted.

If you had it flat earlier, but now it is twisted, it may have been on top of a stack, with the bottom up, which lost moisture, or face up gained moisture. But your goal now it to dry the face. You may be able to place it out in the Sun, or use a heat-gun or blow dryer. If you have a small space heater, you can make a little tent with a tarp blowing under into it. But try to have it only heating the convex face, and check it fairly often.

I'd put a clamp on the high corner of one end, then see how much pressure it takes to push the opposite corner down. This will give you an idea of how much it will be pulling later against your fasteners. You may decide that it doesn't need any kerning if it is easy enough to hold out.
Then think about where is the best location for the fasteners up from the substrate.

Twist does indicate diagonal grain or spiral grain. Such pieces are shrinking or swelling in all three directions--it is a three dimensional situation. Cutting a diagonal kerf can help in two directions, but not in all three, so it is likely that you will still have lengthwise shrinkage and undesired warping with seasonal changes in moisture.

So, if you can straighten it now and you make something, how upset will you be and how much time and effort will be lost if it still misbehaves? I suspect enough so that this board should be discarded for now.

Note that it is impossible to bend a piece flat unless you bend it further than flat. If you bend this 5/8" on 74" flat, when you take off the force, it will go back to 5/8", as it has a memory (or some would say that wood is elastic with small bends). Wood has spring to it, so you need to go beyond flat...quite a bit more. Second, the piece will still have its memory of wanting to twist. That is, bending does not cause the diagonal or spiral grain to go away. Third, dry wood is so strong that to bend it when dry is very difficult; you will need to go back to about 20% MC to get a piece that will bend with a reasonable amount of effort. As mentioned, once you bend it beyond flat, then you have to hold it in that position while it dries. The big trick is estimating how far beyond flat you need to go...you are upset about 5/8" in a 74" span which is not a lot, but certainly is unacceptable. What you need is better than that, so we need more than just a rough estimate.

The forces that make lumber twist and cup are quite large. The proof of this is when you look at a stack of lumber that has been dried and see cup and twist within a stack (sometimes even near the bottom) that has been well stacked. As more proof, try and stand on a piece of lumber that is cupped or twisted and make it go straight with several hundred pounds...won't happen.

I went ahead with the twisted, but beautiful board. If I need to revisit this top in the future, I need to revisit it. I used twelve buttons from below for mehanical strength along the length of the center board, the one in question. I kerfed the bottom and edge-glued it to straight boards on the outside.

Two pics attached.

If it fails, I will let you all know that I should have taken advice to use a different board.

WOODWEB is a professional industrial woodworking site. Hobbyist and homeowner woodworking questions are inappropriate.

Messages should be kept reasonably short and on topic, relating to the focus of the forum. Responses should relate to the original question.

A valid email return address must be included with each message.

Advertising is inappropriate. The only exceptions are the Classified Ads Exchange, Machinery Exchange, Lumber Exchange, and Job Opportunities and Services Exchange. When posting listings in these areas, review the posting instructions carefully.

Subject lines may be edited for length and clarity.

"Cross posting" is not permitted. Choose the best forum for your question, and post your question at one forum only.

Messages requesting private responses will be removed - Forums are designed to provide information and assistance for all of our visitors. Private response requests are appropriate at WOODWEB's Exchanges and Job Opportunities and Services.

Messages that accuse businesses or individuals of alleged negative actions or behavior are inappropriate since WOODWEB is unable to verify or substantiate the claims.

Posts with the intent of soliciting answers to surveys are not appropriate. Contact WOODWEB for more information on initiating a survey.

Excessive forum participation by an individual upsets the balance of a healthy forum atmosphere. Individuals who excessively post responses containing marginal content will be considered repeat forum abusers.

Responses that initiate or support inappropriate and off-topic discussion of general politics detract from the professional woodworking focus of WOODWEB, and will be removed.

Participants are encouraged to use their real name when posting. Intentionally using another persons name is prohibited, and posts of this nature will be removed at WOODWEB's discretion.

Carefully review your message before clicking on the "Send Message" button - you will not be able to revise the message once it has been sent.

You will be notified of responses to the message(s) you posted via email. Be sure to enter your email address correctly.

WOODWEB's forums are a highly regarded resource for professional woodworkers. Messages and responses that are crafted in a professional and civil manner strengthen this resource. Messages that do not reflect a professional tone reduce the value of our forums.

Messages are inappropriate when their content: is deemed libelous in nature or is based on rumor, fails to meet basic standards of decorum, contains blatant advertising or inappropriate emphasis on self promotion (return to top).

Libel: Posts which defame an individual or organization, or employ a tone which can be viewed as malicious in nature. Words, pictures, or cartoons which expose a person or organization to public hatred, shame, disgrace, or ridicule, or induce an ill opinion of a person or organization, are libelous.

Improper Decorum: Posts which are profane, inciting, disrespectful or uncivil in tone, or maliciously worded. This also includes the venting of unsubstantiated opinions. Such messages do little to illuminate a given topic, and often have the opposite effect. Constructive criticism is acceptable (return to top).

Advertising: The purpose of WOODWEB Forums is to provide answers, not an advertising venue. Companies participating in a Forum discussion should provide specific answers to posted questions. WOODWEB suggests that businesses include an appropriately crafted signature in order to identify their company. A well meaning post that seems to be on-topic but contains a product reference may do your business more harm than good in the Forum environment. Forum users may perceive your references to specific products as unsolicited advertising (spam) and consciously avoid your web site or services. A well-crafted signature is an appropriate way to advertise your services that will not offend potential customers. Signatures should be limited to 4-6 lines, and may contain information that identifies the type of business you're in, your URL and email address (return to top).

There are often situations when the original message asks for opinions: "What is the best widget for my type of shop?". To a certain extent, the person posting the message is responsible for including specific questions within the message. An open ended question (like the one above) invites responses that may read as sales pitches. WOODWEB suggests that companies responding to such a question provide detailed and substantive replies rather than responses that read as a one-sided product promotion. It has been WOODWEB's experience that substantive responses are held in higher regard by our readers (return to top).

The staff of WOODWEB assume no responsibility for the accuracy, content, or outcome of any posting transmitted at WOODWEB's Message Boards. Participants should undertake the use of machinery, materials and methods discussed at WOODWEB's Message Boards after considerate evaluation, and at their own risk. WOODWEB reserves the right to delete any messages it deems inappropriate. (return to top)

Forum Posting Form Guidelines

Your Name

The name you enter in this field will be the name that appears with your post or response (return to form).

Your Website

Personal or business website links must point to the author's website. Inappropriate links will be removed without notice, and at WOODWEB's sole discretion. WOODWEB reserves the right to delete any messages with links it deems inappropriate. (return to form)

E-Mail Address

Your e-mail address will not be publicly viewable. Forum participants will be able to contact you using a contact link (included with your post) that is substituted for your actual address. You must include a valid email address in this field. (return to form)

Subject

Subject may be edited for length and clarity. Subject lines should provide an indication of the content of your post. (return to form)

Thread Related Link and Image Guidelines

Thread Related Links posted at WOODWEB's Forums and Exchanges should point to locations that provide supporting information for the topic being discussed in the current message thread. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related Link that directs visitors to an area with inappropriate content will be removed. WOODWEB reserves the right to delete any messages with links or images it deems inappropriate. (return to form)

Thread Related File Uploads

Thread Related Files posted at WOODWEB's Forums and Exchanges should provide supporting information for the topic being discussed in the current message thread. Video Files: acceptable video formats are: .MOV .AVI .WMV .MPEG .MPG .FLV .MP4 (Image Upload Tips) If you encounter any difficulty when uploading video files, E-mail WOODWEB for assistance. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related File that contains inappropriate content will be removed, and uploaded files that are not directly related to the message thread will be removed. WOODWEB reserves the right to delete any messages with links, files, or images it deems inappropriate. (return to form)

The editors, writers, and staff at WOODWEB try to promote safe practices.
What is safe for one woodworker under certain conditions may not be safe
for others in different circumstances. Readers should undertake the use
of materials and methods discussed at WOODWEB after considerate evaluation,
and at their own risk.